A control system of Robert Bosch GmbH is widely sold in the marketplace under the name MOTRONIC which is used to adjust especially the ignition angle ZW and the injection time ti. Details of this system are discussed with respect to FIGS. 1 and 2 insofar as they are pertinent to the present invention.
The description of FIG. 1 follows in reference to the adjustment of the injection time ti for steady-state operation. From a precontrol value ROM 20, preliminary injection times tiv are addressed via values of address operating variables, namely, the speed n of the internal combustion engine 21 whose air charge L and engine temperature Tw are read out and transmitted to a corrective logic combining unit 22 which is multiplied by a corrective value K=1 for the steady-state case. The value of the preliminary injection time tiv which is thereby unchanged is supplied to a control logic combining unit 23 which performs a multiplicative logic operation with a control factor FR which is supplied from a control unit 24. In this way, a value of injection time ti is obtained. The control unit 24 determines the control factor FR from the difference of a lambda actual value and a lambda desired value. The lambda actual value is supplied by a sensor unit 25 and the lambda desired value is read out from a desired value ROM 26 when addressed via the above-mentioned addressing operating variables.
If the ignition angle ZW is to be determined in lieu of the injection time ti, preliminary ignition angles ZWv are stored as precontrol values and, instead of the described multiplicative logic combinations, additive logic combinations are performed. The corrective addend for steady-state operation is then 0. The control variable is then the combustion condition VL in lieu of the air ratio lambda.
A status recognition device 27 having a selector switch 28 and a corrective value ROM 29 are shown below the dashed line in FIG. 1. In the corrective value ROM 29, transient-corrective functions f(Z) of actuating variables are stored and are addressable via values of the above-mentioned addressing operation variables and values of the load change dL/dt and the number (Z) of suction strokes since a suction stroke Z=0. The suction stroke having the number Z=0 is that stroke at which the status recognition device determines that the load change dL/dt has exceeded a certain threshold value. As a consequence thereof, the status recognition device 27 delivers a transient signal which sets the number value Z to 0 and which actuates the selector switch 28 such that this switch then connects the corrective value ROM 29 with the corrective logic combining unit 22.
An actuating value transient corrective function as it is stored in the corrective value ROM 29 is shown in FIG. 2. The function comprises a sequence of corrective values K(Z) which in the example is a sequence of N=16 values. The number N of the stored values is dependent primarily on what kind of sensor is utilized for measuring the load changes. If a relatively sluggish sensor is utilized, for example, a suction-pressure measuring device, then N can be 32 instead of 16. The corrective values K(Z) decrease with an increasing number Z of suction strokes. In the example, for Z=15, the corrective value "1" for the multiplicative logic is obtained. This value "1" can be first reached when Z=N=16; however, it can also be reached earlier. The amount of the largest corrective value K(1) and the course of the corrective values is dependent on the values of the addressing operating variables at the point in time of the occurrence of the transient signal, that is, at the point in time at which Z=0. Correspondingly, the addressing operating variables are indexed at the corrective value ROM 29 in FIG. 1 with the number "0 ".
With the MOTRONIC system, the above-mentioned memory and units are part of a microcomputer. For the entire further description, it applies that the memory and function units are advantageously verified by means of a microcomputer. In contrast thereto, sensors and actuators are typical discrete components.
A disadvantage of the control system already described is that the corrective function f(Z) stored in corrective value ROM is are determined for all engines of a specific series without consideration being made for tolerances within a series and without consideration for aging effects.